OpenSUSE might be a good one but you could also experiment with archlinux in a VM learning it really helps in making you more comfortable with GNU/Linux in general. They have good guides and a good wiki.

I use GNU Guix System and I really like how it works. Is it the best? There is no best really but to me those distros with 100% free software are the best. Like Trisquel, Parabola and GNU Guix System

Depends on what you need, if you're a small business you won't need much and it won't cost as much as if you'd run a big business. Anyway, the whole point was to be more self reliant, how is being self reliant a bad thing? Why should you give all your information and trust a third party with everything you have?

I think you could easily hire people who do that job at your company or someone who maintain it at least or some contractors.

Well companies can also have their own servers. It would even be better than relying on a third party where when the company does a mistake then all their clients (other companies) are affected. The Cloudstrike bug would be a good example of that.